Clive Ure wrote:
 Paul,

 Are there any types of 20B engine that are 'lemons' that
 I should not consider for my 337 project. Any years better than
 others?

 Regards

 Clive

 Not that I know of. The only rotary engine I know that might be
 labeled a lemon
 was the 2004-2006 RX8 engine and it had nothing to do with the engine
 it self. Mazda merely cut back too far on the apex seal oil supply.
 Fixed around 2007 with three instead of two oil injectors per rotor.
 Of course
 we mix 2 cycle oil in the fuel to bypass that situation.

 The 1989-1990 initial Turbo II engine cracked the exhaust manifold
 with regularity. Fixed more or less in the 1991-1992 Turbo II engines.

 A lot of Turbo 3rd gen guys blew them up by boosting the engine
 without adjusting the fuel supply. They ran lean. The 3 piece apex seal
 design did not help. Done away with in the RX8 engine with a 2
 piece design now retrofitted to all engines.

 Paul Lamar

 Thanks Paul,

 1.Shall I use the existing turbo(s), I want to turbo normalize so I
 want to modify the waste gate to manual operation controlled by the
 pilot.

 2.I would like to use the existing injectors? and the computer to
 control them or do you suggest something else?

 3.I like the slide throttle concept like the one attached here, is
 there anyone who can make one for me?

 I have read Tracy's book and your 'cooling' book.

 I really value your opinion.

 Thanks

 Clive

 You might have trouble with the stock turbo's. They are not
 up to continuous high power. Especially at 12K and above where
 the back pressure is down. They tend to over rev and the turbines
 blow. At least that happened on the turbo 2 rotors.
 I would change them out for one AC turbo.

 Tome Parkes on here has a 3 rotor with an AC turbo in a Lancair ES.

 Paul Lamar


Sorry for my ignorance...what is an "AC Turbo"?  Thanx...

Gene Kahn

Sorry I should have spelled it out. I meant AirCraft turbo.

Aircraft turbochargers come in different combinations compared to an
automotive
turbo. A turbocharger in a car is designed for rapid turbine RPM
acceleration
and intermittent use. This is done in several ways. An exhaust gas
nozzle is built in to speed up the exhaust gases before they impinge
on the turbine.  The diameter of the turbine and the diameter of the
compressors are adjusted to have this happen. What results is a
turbocharger
design that will over speed and blow up if the engine is run at
80% power for hours on end. Exactly what is required of an aircraft engine.

Another factor is what happens when you climb.
Sea Level pressure is about 15 psi. Exhaust gas pressure can be 30 psi
or more. That means the turbine is seeing a only a 15 psi pressure
differential
across the turbine at sea level. If you climb to 12,000 feet air pressure
drops so the pressure across the turbine increases to say 20 psi. That
causes the turbo charger RPM to speed up and may exceed the red line on
the turbine so the blades may fly off.

The same parts and materials are used in aircraft turbo chargers but the
diameters of turbine and compressor are adjusted and or the nozzle so the
turbine will not exceed the RPM red line under high altitude conditions
for hours on end.

The stock Mazda waste gate is a device that is supposed to prevent this but
it is not effective enough for aircraft use. It can be locked wide
open on a stock Mazda turbo charged engine and the turbine will still fail
in just a few hours at 12,000 feet.

I recommend a book called Turbochargers by Hugh Macinnes H.P. Books.
http://www.amazon.com/Hugh-MacInnes/e/B001KML952/ref=ntt_athr_dp_pel_1

Paul Lamar


Paul,


    It seems to me that what  is needed is a section sandwiched
between the exhaust and compressor sections of the turbocharger to
incorporate a sixteen to one  double gear reduction gear set with gears
similar to the paxton or mucullough crank driven superchargers. The driven
shaft would be 1" diameter with cogged belt drive back to the e-shaft. The
engine provides the supercharging acceleration on takeoff and at high RPM
the engine is turbo compound back thru the reduction shaft. The initial
gearset would be 6 to 1 to reduce centrifical force on the large gear. There
is already lubrication plumbed into many turbocharger center housings and
the  added shaft would basically be a shaft extensinn with a small thin gear
in it's center. The housing would  have to be cast iron due to temperature
cycling. Probably CNC cut out of foundary billet stock. As long as the
turbocharger is   geared to the engine it can't overspeed so the wast gate
is a throw away with it's weight offsetting the weight if the added parts.

george grimes

Introducing anything between the compressor and the turbine is a real
can of worms. Several very large companies have been down that road
with a noticeable lack of success. There is a thing called a whirl
mode of vibration when you have what amounts to two flywheels on either
end of a shaft. Also the temperature environment is very high.

That is why I chose to bypass that approach and take power out
of the compressor end  of the turbo with a flexible coupling.

I would use a multi V belt to decouple the torsional vibration
fed back into the gear box from the e-shaft.

http://www.rotaryeng.net/turbo-compound.html

Paul Lamar